Modulation of human checkpoint kinase Chk1 by the regulatory β-subunit of protein kinase CK2

Abstract

Protein kinase CK2 is a serine/threonine protein kinase involved in various aspects of cellular regulation. The regulatory -subunit of CK2 exerts a central role not only in mediating formation of tetrameric CK2 complexes but also as a docking partner for several protein kinases. In this study, CK2 is found to interact with the human cell cycle checkpoint kinase Chk1. The Chk1-interacting region of CK2 is localized at the C-terminus and the complex between CK2 and Chk1 is devoid of the catalytic CK2-subunit. The interaction between CK2 and Chk1 leads to an increase in the Cdc25C phosphorylation activity of Chk1. The screening of several cell lines has revealed that the association between CK2 and Chk1 also occurs in vivo at a different degree. Collectively, these studies confirm the implication of the regulatory -subunit of protein kinase CK2 in cell cycle regulation and identify a novel mechanism for the activation of Chk1 protein kinase.